Wrong time.sleep if time < 17ms

[D.Umbricht]

 Hi all
I try to move a go program from a raspberry pi to an arduino uno using 
tinygo on the arduino.
The program works basically but there's one problem.
For the multiplexing of LED's I use the time.sleep function.
With time.sleep(17*time.Milliseconds) the delay is appr. 17ms.
However whenever the sleep time is < 17ms it actually the delay is only 
appr. 50us.
I assume a problem in the time library but are not an expert.

$tinygo version
tinygo version 0.19.0 linux/amd64 (using go version go1.16.7 and LLVM 
version 11.0.0)

I use the following test program:
package main

import (
    "machine"
    "time"
)

var gpio = []machine.Pin{
        machine.ADC0,
        machine.ADC1,
        machine.D2,
        machine.D3,
        machine.D4,
        machine.D5,
}


func main() {

    // define gpio as output and set them LOW
    for i := 0; i < len(gpio); i++ {
        gpio[i].Configure(machine.PinConfig{Mode: machine.PinOutput})
        gpio[i].Low()
    }


  for {
       gpio[0].High()  // pulse is app. 4us wide
       gpio[0].Low()

       gpio[1].High()
       time.Sleep(time.Millisecond*50) // sleep time appr. 33.9ms
       gpio[1].Low()

       gpio[2].High()
       time.Sleep(50*time.Microsecond) // sleep time appr. 52us
       gpio[2].Low()

       gpio[3].High()
       time.Sleep(17*time.Millisecond) // sleep time appr. 17ms
       gpio[3].Low()

       gpio[4].High()
       time.Sleep(16*time.Millisecond) // sleep time appr. 48us
       gpio[4].Low()


    } //end forloop
} //end

gcc version 5.4.0 (GCC)
avr-libc/focal,focal,now 1:2.0.0+Atmel3.6.1-2 all [installed]

Any help in this matter is very much appreciated.