Your First Program · Lesson 6 of 9

Comments

A free lesson from Swipe Coding · Go, level 2 · updated October 2026

By the Swipe team, founded by Colin · how we make lessons

🤖

Comments are notes for humans — the Go compiler skips right past them. 🐹

A line comment starts with // and runs to the end of that line. The compiler ignores everything after the //, which makes it a quick way to leave a short note for yourself or anyone else reading the code.

// This line explains what happens next
fmt.Println("Hello!") // this comment trails the code

Both comment styles are valid: a // comment on its own line, and a // comment trailing after real code on the same line.

A block comment starts with /* and ends with */, and can span as many lines as you want in between. Block comments are handy for longer explanations, or for temporarily disabling a whole chunk of code without deleting it.

/*
   This entire block
   is ignored by the compiler,
   no matter how many lines it spans.
*/
fmt.Println("Still runs")

Everything between /* and */ is ignored, so only "Still runs" is printed when this code executes.

Quick check

Which comment style can span multiple lines in Go?

Fill in the blank

In Go, everything after ____ on a line is ignored by the compiler, up until the end of that line.

🤖

This convention is how tools like godoc generate documentation automatically. 📚

There's also a convention worth knowing early: a comment written directly above a function or package, starting with that function or package's own name, is treated as documentation by Go's tooling. Following this pattern consistently means your code can generate readable documentation automatically, without any extra effort.

True or false

Comments are compiled into the final executable and can slightly affect how fast a Go program runs.

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