To create and work with custom packages and libraries in Go, follow these steps:
Create a new directory for your package/library. This directory should be named after the package you want to create.
Inside the package directory, create one or more Go source files with a .go extension. These files will contain the functions, types, and variables that make up your package. For example, if your package is called "mylib", you could create a file called mylib.go.
Define your package in the source files using the package declaration. For example, if your package is called "mylib", the first line of your source file should be package mylib. This ensures that other Go files can import and use your package.
Organize your package code into logical files, directories, and packages. It is good practice to group related code together and provide a clear directory structure.
Export functions, types, and variables that you want other packages to use by capitalizing their names. By default, Go considers a name starting with a lowercase letter as unexported, meaning it can only be accessed within the same package. Exported names make them accessible to other packages.
Import your custom package or library in other Go files or applications that need to use it. To do this, use the import keyword followed by the path to the directory containing your package. For example, if your package is contained in the directory /path/to/mylib, you would import it as import "/path/to/mylib".
Once your package is imported, you can use the functions, types, and variables defined in it. You can call package functions, use package types to declare variables, and access package variables in your code.
You can also create separate test files with a _test.go suffix within your package directory to write tests for your package. These test files should contain functions with names starting with Test and should use the testing package for assertions and running tests.
To make your package executable, you can create a main package and define a main function in the package directory. This allows you to build and run your package as an executable program that can be invoked from the command line.
Use the Go toolchain commands like go build or go install to build your package and create an executable or a library file. For example, running go build in your package directory will create an executable file with the same name as the directory.
That's it! You now know how to create and work with custom packages and libraries in Go. Remember to follow Go's idiomatic style and documentation practices to create clean, reusable, and maintainable packages.