I found the missing clue by running `brew info go`, which says:

    ==&gt; Caveats
    A valid GOPATH is required to use the `go get` command.
    If $GOPATH is not specified, $HOME/go will be used by default:
      https://golang.org/doc/code.html#GOPATH

From that I found the executable in question at `$HOME/go/bin`.

I had a similar problem which is why I found your question.  However, in my case I did not have an empty GOPATH but one with multiple directories.  I worked out the issue and describe it here...

If you run go get and you already have the package it says nothing (even with the -v option).  This is confusing if it&#39;s not in the first directory of your GOPATH.  Ie you run go get &lt;whatever&gt;, there is no error or any message but when you check the first directory of the GOPATH (which is where the doc says it should be) you can&#39;t find it.

I eventually found it, but since I have a large GOPATH this was rather tedious.


```
go env
```
you can get the path from `GOMODCACHE`

I am trying to leverage Akka&#39;s finite state machine framework for my use case. I am working on a system that processes a request that goes through various states.

The request here is the application name that needs to be deployed along with the application it depends on:

    Request for application A -&gt; A is in a QUEUED state
    Discover A&#39;s dependency B -&gt; B is in a QUEUED state
    B is being processed -&gt; B is in a PROCESSING STATE
    A is being processed -&gt; A is in a PROCESSING STATE
    B is processed -&gt; B is in a DONE state
    A is processed -&gt; A is in a DONE state

For this I am initializing a finite state machine at discovery time. So `A`&#39;s FSM is created when the request comes in, `B`&#39;s FSM is initialized when `B` is discovered from one of the actors.

Do I initialize and pass the FSM instance to all the actors, and at the same time `tell` the FSM about the operations being performed on the data so that the state machine goes in the correct state?

Here is the relevant portion of the state machine:

    when(QUEUED, matchEvent(requestAccepted.class, MyApp.class,
        (requestAccepted, service) -&gt; 
        goTo(PROCESSING).replying(PROCESSING)));
    
    when(PROCESSING, matchEvent(completed.class, MyApp.class,
        (completed, service) -&gt; goTo(DONE).replying(DONE)));

    // During transitions, save states in the database.
    onTransition(matchState(PROCESSING, DONE, () -&gt; {
      nextStateData().setServiceStatus(DONE);
      databaseWriter.tell(nextStateData(), getSelf());

And here is an example from one of the actors processing the request:

    ProcessingActor extends AbstractActor {
    
        @Override
          public void onReceive(Object message) throws Throwable {
            if (message instanceof processApplication) {
             // process the app
             // Initialize FSM for the Application
             FSM myFSM = Props.create(MYFSM.class);
             myFSM.tell( new completed(processApplication.app)
        }

Is this the right way to initialize the state machine and use it? Or should the initialization happen in the constructor of the `ProcessingActor`? But in that case there wouldn&#39;t be one state machine per application (data).


Akka finite state machine instances

Python 3.7 was released a while ago, and I wanted to test some of the fancy new `dataclass`+typing features. Getting hints to work right is easy enough, with both native types and those from the `typing` module:

    &gt;&gt;&gt; import dataclasses
    &gt;&gt;&gt; import typing as ty
    &gt;&gt;&gt; 
    ... @dataclasses.dataclass
    ... class Structure:
    ...     a_str: str
    ...     a_str_list: ty.List[str]
    ...
    &gt;&gt;&gt; my_struct = Structure(a_str=&#39;test&#39;, a_str_list=[&#39;t&#39;, &#39;e&#39;, &#39;s&#39;, &#39;t&#39;])
    &gt;&gt;&gt; my_struct.a_str_list[0].  # IDE suggests all the string methods :)

But one other thing that I wanted to try was forcing the type hints as conditions during runtime, i.e. it should not be possible for a `dataclass` with incorrect types to exist. It can be implemented nicely with [`__post_init__`](https://www.python.org/dev/peps/pep-0557/#post-init-processing):

    &gt;&gt;&gt; @dataclasses.dataclass
    ... class Structure:
    ...     a_str: str
    ...     a_str_list: ty.List[str]
    ...     
    ...     def validate(self):
    ...         ret = True
    ...         for field_name, field_def in self.__dataclass_fields__.items():
    ...             actual_type = type(getattr(self, field_name))
    ...             if actual_type != field_def.type:
    ...                 print(f&quot;\t{field_name}: &#39;{actual_type}&#39; instead of &#39;{field_def.type}&#39;&quot;)
    ...                 ret = False
    ...         return ret
    ...     
    ...     def __post_init__(self):
    ...         if not self.validate():
    ...             raise ValueError(&#39;Wrong types&#39;)

This kind of `validate` function works for native types and custom classes, but not those specified by the `typing` module:

    &gt;&gt;&gt; my_struct = Structure(a_str=&#39;test&#39;, a_str_list=[&#39;t&#39;, &#39;e&#39;, &#39;s&#39;, &#39;t&#39;])
    Traceback (most recent call last):
	  a_str_list: &#39;&lt;class &#39;list&#39;&gt;&#39; instead of &#39;typing.List[str]&#39;
      ValueError: Wrong types

Is there a better approach to validate an untyped list with a `typing`-typed one? Preferably one that doesn&#39;t include checking the types of all elements in any `list`, `dict`, `tuple`, or `set` that is a `dataclass`&#39; attribute.

---

Revisiting this question after a couple of years, I&#39;ve now moved to use [`pydantic`](https://pydantic-docs.helpmanual.io/) in cases where I want to validate classes that I&#39;d normally just define a dataclass for. I&#39;ll leave my mark with the currently accepted answer though, since it correctly answers the original question and has outstanding educational value. 

Validating detailed types in python dataclasses

I&#39;ve been given instructions to run `go get &lt;some-remote-git-repo&gt;` which seems to succeed, but it&#39;s not clear to me where the package was installed to so I can run an executable from it.

Per https://golang.org/doc/code.html#remote it seems it will be installed in `$GOPATH/bin` but `$GOPATH` isn&#39;t defined in my shell (though the `go get` command seems to work fine). Go is installed via Homebrew.

Where does go get install packages?

<p>I've been given instructions to run <code>go get &#x3C;some-remote-git-repo></code> which seems to succeed, but it's not clear to me where the package was installed to so I can run an executable from it.</p>
<p>Per <a href="https://golang.org/doc/code.html#remote" target="_blank" rel="noopener noreferrer">https://golang.org/doc/code.html#remote</a> it seems it will be installed in <code>$GOPATH/bin</code> but <code>$GOPATH</code> isn't defined in my shell (though the <code>go get</code> command seems to work fine). Go is installed via Homebrew.</p>


Hi I&#39;m trying to retrieve the function/method of one struct but I&#39;m using an interface as parameter and using this interface I&#39;m trying to access the function of the struct. To demonstrate what I want below is my code

    // Here I&#39;m trying to use &quot;GetValue&quot; a function of RedisConnection but since &quot;c&quot; is an interface it doesn&#39;t know that I&#39;m trying to access the RedisConnection function. How Do I fix this?
    func GetRedisValue(c Connection, key string) (string, error) {
    	value, err := c.GetValue(key)

    	return value, err
    }

    // Connection ...
    type Connection interface {
	    GetClient() (*redis.Client, error)
    }

    // RedisConnection ...
    type RedisConnection struct {}

    // NewRedisConnection ...
    func NewRedisConnection() Connection {
	    return RedisConnection{}
    }

    // GetClient ...
    func (r RedisConnection) GetClient() (*redis.Client, error) {
	    redisHost := &quot;localhost&quot;
    	redisPort := &quot;6379&quot;

    	if os.Getenv(&quot;REDIS_HOST&quot;) != &quot;&quot; {
	    	redisHost = os.Getenv(&quot;REDIS_HOST&quot;)
    	}

	    if os.Getenv(&quot;REDIS_PORT&quot;) != &quot;&quot; {
    		redisPort = os.Getenv(&quot;REDIS_PORT&quot;)
	    }

    	client := redis.NewClient(&amp;redis.Options{
	    	Addr:     redisHost + &quot;:&quot; + redisPort,
		    Password: &quot;&quot;, // no password set
    		DB:       0,  // use default DB
	    })

    	return client, nil
    }

    // GetValue ...
    func (r RedisConnection) GetValue(key string) (string, error) {
	    client, e := r.GetClient()
    	result, err := client.Ping().Result()
    	return result, nil
    }

Golang Cast interface to struct

I have an outer and inner loop, each iterating over a range. I want to exit the outer loop when a condition is satisfied inside the inner loop.

I have a solution which works using two &#39;break&#39;s, one inside the inner loop and one inside the outerloop, just outside the inner loop (a very simplified case for demonstration):

    package main
    
    import (
    	&quot;fmt&quot;
    )
    
    func main() {
    	
    	word := &quot;&quot;
    	for _, i := range(&quot;ABCDE&quot;) {
    		for _,j := range(&quot;ABCDE&quot;) {
    			word = string(i) + string(j)
    			fmt.Println(word)
    			if word == &quot;DC&quot; {
    				break
    			}
    		}
    		if word == &quot;DC&quot; {
    			break
    		}
    	}
    	// More logic here that needs to be executed
    }
[Go Playground][1]

There is no problem with this solution, but it just looks patched and ugly to me. Is there a better way to do this?

I can try and have another for conditional loop outside the outer loop in the previous solution and have a label and use continue with the label. But as you can see, this approach isn&#39;t any more elegant than the solution with break.

    package main
    
    import (
    	&quot;fmt&quot;
    )
    
    func main() {
    
    	word := &quot;&quot;
    
    Exit:
    	for word != &quot;DC&quot; {
    		for _, i := range &quot;ABCDE&quot; {
    			for _, j := range &quot;ABCDE&quot; {
    				word = string(i) + string(j)
    				fmt.Println(word)
    				if word == &quot;DC&quot; {
    					continue Exit
    				}
    			}
    		}
    	}
    	// More logic here that needs to be executed
    }
[Go Playground][2]

I have seen similar questions here pertaining to other languages (C, C#, Python etc). But what I am really interested to see is whether there is any trick with Go constructs such as &#39;for select&#39;.


  [1]: https://play.golang.org/p/URY29ukzp9A
  [2]: https://play.golang.org/p/cWrqtDV34L4

How to break out of nested loops in Go?

I&#39;m trying out Go&#39;s new modules system and am having trouble accessing local packages. The following project is in a folder on my desktop outside my gopath.

My project structure looks like:

    /
      - /platform
          - platform.go
      - main.go
      - go.mod

----

    // platform.go
    package platform
    
    import &quot;fmt&quot;

    func Print() {
        fmt.Println(&quot;Hi&quot;)
    }


---

    // main.go
    package main
    
    import &quot;platform&quot;

    func main() {
        platform.Print()
    }

`go build main.go` tells me

    cannot find module for path platform

Accessing local packages within a go module (go 1.11)

As we all know, panics produce a stacktrace to stdout ([Playground link][1]).:

    panic: runtime error: index out of range
    goroutine 1 [running]:
    main.main()
    	/tmp/sandbox579134920/main.go:9 +0x20

And it seems when you recover from a panic, `recover()` returns only an `error` which describes what caused the panic ([Playground link][2]). 

    runtime error: index out of range

My question is, is it possible to store the stacktrace which is written to stdout? This provides much better debugging information than the string `runtime error: index out of range` because it shows the exact line in a file which caused the panic.


  [1]: https://play.golang.org/p/b-Uz6eTkVJ-
  [2]: https://play.golang.org/p/7qsB3F2klUb

How to get the stacktrace of a panic (and store as a variable)

I tried this code in Go:

    type Agent struct {
        name string    // Not exported
        categoryId int // Not exported
    }

And VS Code reports the following *problem*:

&gt; exported type Agent should have comment or be unexported

&lt;br&gt;
The warning is kind of annoying. So I have the following questions:

 - How to get rid of it?
 - What comment should I put?
 - Is there any *default* comment template for this?

It asks me to put a comment but it does not offer me to add one by default.

&quot;Exported type should have comment or be unexported&quot; golang VS Code

How can I install a previous version of Python 3 in macOS using brew?

With the command `brew install python` I got the latest version of Python 3 (currently v3.7.0), but I want the last version of Python 3.6 (currently 3.6.5).

I have read about another package `pyenv` that can assist in handle different python installation, but this solution is not suitable for me.

How can I install a previous version of Python 3 in macOS using homebrew?

After NGINX upgrade to `v1.15.2` starts getting the warning.

`nginx: [warn] the &quot;ssl&quot; directive is deprecated, use the &quot;listen ... ssl&quot; directive instead in /usr/local/etc/nginx/sites-enabled/confid-file-name:8`

Where the 8th line is `ssl on;`

how I can solve this?

nginx the &quot;ssl&quot; directive is deprecated, use the &quot;listen ... ssl&quot;

I tried to install Valgrind with `brew install Valgrind` and got  :

    valgrind: This formula either does not compile or function as expected
    on macOS versions newer than Sierra due to an upstream
    incompatibility. 
    Error: An unsatisfied requirement failed this build.

I tried  `brew install --HEAD Valgrind`. 

Instead, after successfully installing the dependencies `autoconf`, `automake` and `libtool`, when it tries to install valgrind, I get a configure error:

    Valgrind works on Darwin 10.x, 11.x, 12.x, 13.x, 14.x, 15.x, 16.x and
    17.x (Mac OS X 10.6/7/8/9/10/11 and macOS 10.12/13)

My OS is macOS Mojave(10.14), so does it mean that I can&#39;t install a functioning Valgrind with Homebrew presently?

How to install Valgrind on macOS Mojave(10.14) with Homebrew?

I installed node using homebrew (Mojave), afterwards php stoped working and if I try to run `php -v` I get this error:

    php -v
    dyld: Library not loaded: /usr/local/opt/icu4c/lib/libicui18n.62.dylib
      Referenced from: /usr/local/bin/php
      Reason: image not found

I tried to uninstall both node and icu4c but the problem persists

dyld: Library not loaded: /usr/local/opt/icu4c/lib/libicui18n.62.dylib error running php after installing node with brew on Mac

I was trying to run `brew doctor` but system popped up error of

&gt; /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in
&gt; `require&#39;: cannot load such file --
&gt; active_support/core_ext/object/blank (LoadError)

Searched online and another post suggested to just &quot;gem install activesupport&quot; but then I ran into error of:

    ERROR:  Error installing activesupport:
    	i18n requires Ruby version &gt;= 2.3.0.

I also tried to rvm install ruby-2.3.0 but the same error popped again

    [2019-02-26 10:07:41] requirements_osx_brew_libs_install
    requirements_osx_brew_libs_install ()  { 
        brew install &quot;$@&quot; --force || { 
            \typeset ret=$?;
            requirements_osx_brew_libs_error &quot;installation&quot;;
            return $ret
        } } current path: /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib
    PATH=/Users/{user_name}/.aw/pex_resources/scripts/binaries:/usr/local/sbin:/Users/fengjiao/.rbenv/shims:/Users/{user_name}/.nvm/v0.10.32/bin:/Users/fengjiao/bin:/usr/local/sbin:/usr/local/bin:/Users/{user_name}/.rbenv/shims:/Users/{user_name}/.nvm/v0.10.32/bin:/Users/{user_name}/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/munki:/opt/X11/bin:/Users/fengjiao/gocode/bin:/Users/{user_name}/.rvm/bin
    command(10): requirements_osx_brew_libs_install autoconf automake
    libtool pkg-config coreutils libyaml readline libksba openssl@1.1
    ++ brew install autoconf automake libtool pkg-config coreutils libyaml readline libksba openssl@1.1 --force
    /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in
    `require&#39;: cannot load such file --
    active_support/core_ext/object/blank (LoadError) 	from
    /System/Library/Frameworks/Ruby.framework/Versions/2.3/usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in
    `require&#39; 	from /usr/local/Homebrew/Library/Homebrew/global.rb:10:in
    `&lt;top (required)&gt;&#39; 	from
    /usr/local/Homebrew/Library/Homebrew/brew.rb:21:in `require_relative&#39;
    	from /usr/local/Homebrew/Library/Homebrew/brew.rb:21:in `&lt;main&gt;&#39;
    ++ typeset ret=1
    ++ requirements_osx_brew_libs_error installation
    ++ rvm_warn &#39;There were package installation errors, make sure to read the log.
    
    Try `brew tap --repair` and make sure `brew doctor` looks reasonable.

Content Type	Original Author	Original Content on Stackoverflow
Question	Liron Yahdav	View Question on Stackoverflow
Solution 1 - Go	Liron Yahdav	View Answer on Stackoverflow
Solution 2 - Go	Andrew W. Phillips	View Answer on Stackoverflow
Solution 3 - Go	Daisy	View Answer on Stackoverflow

Where does go get install packages?

Go Problem Overview

Go Solutions

Solution 1 - Go

Solution 2 - Go

Solution 3 - Go

Validating detailed types in python dataclasses

Akka finite state machine instances

Attributions