$ go build foo.go 
# command-line-arguments
./foo.go:6: invalid operation: 1 << uint(bar.f·2) (shift of type float64)
./foo.go:10: tempname called with nil type
./foo.go:10: cannot use autotmp_0001 (type int32) as type float64 in assignment

package main

import (
    "fmt"

    "bar"
)

func main() {
    fmt.Println(bar.Baz(2))
}

package bar

func Baz(f int) float64 {
    return 1 / float64(int(1)<<(uint(f)))
}