I have Xcode 11 installed on my Mojave system (10.14.6). But Xcode doesn't let me choose Swift 5.1. What am I missing?
Xcode 11 comes with Swift 5.1 compiler (even on Mojave) and you can easily check it with writing code with some Swift 5.1 feature.
func myFunc() -> String {
"abc"
}
(SE-0255 Implicit returns from single-expression functions)
Just choose Swift 5
and you can use Swift 5.1 features.