04-go-duration-formatting.md

Go time.Duration Formatting

Problem

In Go, there is a useful data type called time.Duration, which is typically used to represent time intervals, such as request latency.

However, the default String() method doesn’t always return a concise output. For instance, the following code might generate an unnecessarily long string:

fmt.Printf("Total duration: %s\n", totalDuration)

Total duration: 5.66225375s

What if I don’t need this level of nanosecond precision? Is there a way to display the duration in milliseconds only?

Solution

We can use either Round() or Truncate() methods to achieve the desired level of precision.

In this case, I am using Round() to keep the milliseconds only:

fmt.Printf("Total duration: %s\n", totalDuration.Round(time.Millisecond))

Now, the value is formatted neatly:

Total duration: 5.662s

Examples from Round() documentation show how it can be used to format time.Duration:

d.Round(   1ns) = 1h15m30.918273645s
d.Round(   1µs) = 1h15m30.918274s
d.Round(   1ms) = 1h15m30.918s
d.Round(    1s) = 1h15m31s
d.Round(    2s) = 1h15m30s
d.Round(  1m0s) = 1h16m0s
d.Round( 10m0s) = 1h20m0s
d.Round(1h0m0s) = 1h0m0s