Go/src/builtin/builtin.go:52
// int64 is the set of all signed 64-bit integers.
// Range: -9223372036854775808 through 9223372036854775807.
type int64 int64
Go/src/time/time.go:590
// A Duration represents the elapsed time between two instants
// as an int64 nanosecond count. The representation limits the
// largest representable duration to approximately 290 years.
type Duration int64
package time
// Sleep pauses the current goroutine for at least the duration d.
// A negative or zero duration causes Sleep to return immediately.
func Sleep(d Duration)
Go/src/time/sleep.go:9