How do if, for, and switch statements work in Go?

// if with an init statement — err is only in scope inside the if block
if err := doWork(); err != nil {
    log.Fatal(err)
}

// for — C-style
for i := 0; i < 5; i++ { fmt.Println(i) }

// for as while
n := 1
for n < 128 { n *= 2 }

// for — infinite loop (use break or return to exit)
for {
    if done() { break }
    doWork()
}

// for range — slices, maps, strings, channels
fruits := []string{"apple", "banana", "cherry"}
for i, fruit := range fruits {
    fmt.Printf("%d: %s\n", i, fruit)
}
for _, fruit := range fruits { fmt.Println(fruit) }  // ignore index

// switch — no implicit fallthrough
switch day {
case "Sat", "Sun":
    fmt.Println("Weekend")
case "Mon", "Tue", "Wed", "Thu", "Fri":
    fmt.Println("Weekday")
default:
    fmt.Println("Unknown")
}

// switch with no expression — replaces long if-else chains
switch {
case score >= 90: fmt.Println("A")
case score >= 80: fmt.Println("B")
default:          fmt.Println("C or below")
}