What is it

// comparison operator
if condition == "true" { 
  ... 
}

// logical NOT operator
if !condition == "true" {
  ...
}

// logical AND
if ( a && b ) {
  fmt.Printf("Condition is true")
}

// logical OR
if ( a || b ) {
  fmt.Printf("Condition is true")
}

if, else if, else

if num := 9; num < 0 {
  fmt.Println(num, "is negative")
} else if num < 10 {
  fmt.Println(num, "has 1 digit")
} else {
  fmt.Println(num, "has multiple digits")
}