Go的switch語句默認(rèn)不會(huì)貫穿執(zhí)行，匹配到第一個(gè)條件後自動(dòng)退出。 1. switch以關(guān)鍵字開始並可帶一個(gè)值或不帶值；2. case按順序從上到下匹配，僅運(yùn)行第一個(gè)匹配項(xiàng)；3. 可通過逗號(hào)列出多個(gè)條件來匹配同一case；4. 不需要手動(dòng)添加break，但可用fallthrough強(qiáng)制貫穿；5. default用於未匹配到的情況，通常放最後。

The switch statement in Go works a bit differently compared to other languages like C or JavaScript, but it's designed to be clean and intuitive once you get used to its style. Unlike some languages where you have to break every case to avoid fall-through, Go doesn't do that by default — which can be both helpful and a source of confusion if you're coming from another language.

Here's how it really works:

Basic syntax and flow

A switch in Go starts with the keyword switch , followed by a value to compare. Then come the case s — each one checks against that value. The first matching case runs, and then it exits the switch block automatically.

For example:

 fruit := "apple"

switch fruit {
case "apple":
    fmt.Println("It's an apple!")
case "banana":
    fmt.Println("It's a banana.")
default:
    fmt.Println("Unknown fruit")
}

This will print:
"It's an apple!"

You don't need to write break at the end of each case — Go does that for you. That helps prevent accidental fall-through bugs.

Multiple conditions in one case

If you want a single case to match multiple values, just list them separated by commas.

Like this:

 letter := "a"

switch letter {
case "a", "e", "i", "o", "u":
    fmt.Println("It's a vowel.")
default:
    fmt.Println("Not a vowel.")
}

In this example, since letter is "a" , it will print:
"It's a vowel."

This is super handy when grouping similar cases without repeating code.

Using switch without a value (like if-else chains)

Go also lets you use a switch without any value — kind of like a cleaner way to write a bunch of if/else if statements.

Example:

 age := 25

switch {
case age < 13:
    fmt.Println("Child")
case age < 20:
    fmt.Println("Teenager")
case age < 30:
    fmt.Println("Young adult")
default:
    fmt.Println("Adult")
}

Since age is 25, it'll print:
"Young adult"

This version is great when checking ranges or complex conditions instead of exact matches.

Also, the order matters here — the first true condition wins, so always start from the most specific.

A few things to remember

• Cases are evaluated top to bottom.
• Only the first matching case runs — no automatic fall-through.
• You can force fall-through using the fallthrough keyword, but it's rarely needed and usually not recommended.
• The default case runs if none of the others match — and it can go anywhere in the block, though it's typically placed last.

So if you ever see something like this:

 switch num := 3; num {
case 3:
    fmt.Println("Three")
    fallthrough
case 2:
    fmt.Println("Two")
}

It will print both "Three" and "Two" , because of fallthrough . But again, this is not common practice.

Basically, Go's switch keeps things simple and safe by default. It avoids many of the classic bugs from forgotten break s, and gives you flexibility when you need more complex logic. Just keep your conditions clear and ordered properly, and it'll work well for most decision-based flows.

That's how the switch statement works in Go — straightforward, but with a few quirks worth knowing.

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