Create Go workspace

Once the Go build environment is ready, the next step is to create workspace for development:

(1) Set up a new empty directory:

# mkdir gowork

(2) Use a new environment variable $GOPATH to point it:

# cat /etc/profile
......
GOPATH=/root/gowork
export GOPATH
...... 

The workspace should contain 3 subdirectories:

src: contains the Go source code.
pkg: contains the package objects. You could think them as libraries which are used in linkage stage to generate the final executable files.
bin: contains the executable files.

Let's see an example:

(1) Create a src directory in $GOPATH, which is /root/gowork in my system:

# mkdir src
# tree
.
└── src

1 directory, 0 files

(2) Since Go organizes source code using "package" concept , and every "package" should occupy a distinct directory, I create a greet directory in src:

# mkdir src/greet

Then create a new Go source code file (greet.go) in src/greet:

# cat src/greet/greet.go
package greet

import "fmt"

func Greet() {
        fmt.Println("Hello 中国!")
}

You can consider this greet directory provides a greet package which can be used by other programs.

(3) Create another package hello which utilizes the greet package:

# mkdir src/hello
# cat src/hello/hello.go
package main

import "greet"

func main() {
        greet.Greet()
}

You can see in hello.go, the main function calls Greet function offered by greet package.

(4) Now our $GOPATH layout is like this:

# tree
.
└── src
    ├── greet
    │   └── greet.go
    └── hello
        └── hello.go

3 directories, 2 files

Let's compile and install hello package:

# go install hello

Check the $GOPATH layout again:

# tree
.
├── bin
│   └── hello
├── pkg
│   └── linux_amd64
│       └── greet.a
└── src
    ├── greet
    │   └── greet.go
    └── hello
        └── hello.go

6 directories, 4 files

You can see the executable command hello is generated in bin folder. Because hello needs greet package's help, a greet.a object is also produced in pkg directory, but in system related subdirectory: linux_amd64.

Run hello command:

# ./bin/hello
Hello 中国!

Working as expected!

(5) You should add $GOPATH/bin to $PATH environment variable for facility:

PATH=$PATH:$GOPATH/bin
export PATH

Then you can run hello directly:

# hello
Hello 中国!

Reference:
How to Write Go Code.