expert-umbrella

An umbrella project for Golang

Driving Force

Learning Golang with applied applications

General Notes

main is special. As a package, it deifnes a standalone executable program and not a library. The function main is where the execution of the main program begins.

import declaration is import as one must import the exact needed packages. A program will NOT compile if there are missing or unnecessary imports.

package declaration -> import declaration -> then everything else

func: Functions require the keyword func, the name of the function, a parameter list, a body, and a result list

Go only requires semicolons when two or more statements or declarations appear on the same line

The location of newlines in Go matter

gofmt tool rewrites code into the standard format. goimports is another helpful tool

Go does not permit unused local variables which would result in a compiliation error

Installing packages

go install golang.org/x/tools/cmd/goimports@latest.

go get is no longer supported and the version, @latest must be explicitly stated

Best Practices

Describe each package with a comment before the package declartion. main packages have comments describing the entire program as a whole.

Use either of the two forms to initialize a variable.

s: = "" var s string The first form is when the inital value matters more, the second is when the data type matter more

Useful Tips

:= is a short variable declaration which allows for the declaration of one or more variable and the assignment of the corresponding type based on the initializer value.

i++ is a numeric increment statement

i-- is a numeric decrement statement

Looping in Go

The for loop os the only loop statement in Go with various forms but with a standard structure and the opening brace must be on the same line as the post.

for initialization; condtion; post {
    //statements here
}

The initialization is optional and is executed before the loop starts. It must be a simple statement being one of the following

A short variable declaration i := 1 An increment or assignment statemnet A function call

The condition is a boolean expression which is evaluated at the beginning of each loop iteration

The post is executed after the body of the loop then the condition is evaluated again.

The loop ends when the condition becomes false.

initialization, condition, post are all option for a loop

A traditional while loop can be constructed as follows

for condition {
    // .. 
}

A traditional infinite loop can be expressed as

for {
    // ..
}

The above can be escaped with a break or return statement

Command-Line Arguments

• The os package provides functions and other values for platform-independent OS interactions.
• Command-line arguments are available to the program in a variable called Args that is part of the os package.

• Use os.args to access the variable outside of the os package
• The variable os.args is a slice of strings. Go Slices will be discussed later but are functionally like a Python List with some differences.
• The first element of os.args, os.args[0], is the name of the command itself. All other elements are the arguments that were present at the start of execution.
• The typical desired slice is os.args[1:]