:= is for both declaration, assignment, and also for redeclaration.
ex) foo := 32 is a shor-hand form of
```
var foo int
foo = 32
```
var foo int = 32
var foo = 32
- cannot ues := out of functions
- cannot use them twice in the same scope
- can use them for multi-variable declarations and assignments foo, bar := 42, 314
- can use the shor decalaration to declared with the same name before var foo int = 34