The HelloWorld of the Go language under the MacBook

• Directory for Go language development
  
  General Go Language $gopath directory conventions have three subdirectories:
• SRC store source code (e.g.,. Go. C. h, etc.)
• The files generated by the PKG after compilation (for example:. a)
• Bin compiled executable file (for convenience, this directory can be added to the $PATH variable, if there are multiple gopath, then use to ${GOPATH//://bin:}/bin Add all bin directory)
• Go Language Development Directory planning
  
  Gopath under the SRC directory is the main directory of the next development program, all the source code is placed under this directory, then generally we practice is a directory of a project, for example: $GOPATH/src/mymath represents mymath this application package or executable application, This is based on whether the package is main or otherwise, and the main word is the executable application, and the other is the app
  
  
• Creation of HelloWorld
  Let's take MyMath as an example of how to write an app package and execute the following code:
  

  CD $GOPATH/srcmkdir MyMath

  Create a new file Sqrt.go with the following content:
  
  

  Package Mymathfunc Sqrt (x float64) float64 {z: = 0.0for I: = 0; i <; i++ {z-= (z*z-x)/(2 * x)}return Z}

  Note: It is generally recommended that the package name and directory name remain the same
  
  At this point, the app package has been created, and the following is the installation of the app package, as in the next two ways:
  
  

  1, just enter the corresponding application package directory, and then execute go install , you can install the

  2. Execute the following code in any directorygo install mymath

  After the installation is complete, pass the command:

  CD $GOPATH/pkg/${goos}_${goarch}

  You can see the file mymath.a

  At this point, the application package has been established, a program to invoke the application package, a new application package Mathapp
  
  

  CD $GOPATH/srcmkdir mathappcd mathappvim main.go

  The source code of Main.go is as follows:
  
  

  Package Mainimport ("MyMath" "FMT") func main () {FMT. Printf ("Hello, World.  ") SQRT (2) =%v\n ", MyMath. SQRT (2))}

  Go to the app's directory and the Go build will generate a Mathapp executable that executes the following command:

  ./mathapp

  You will get the following output:

  Hello, world.  SQRT (2) = 1.414213562373095

　　　

The HelloWorld of the Go language under the MacBook