How Can You Measure Function Runtime in Go Using the `defer` Keyword?

Timing Functions and Calculating Runtime in Go

In Go, you can utilize the time package to accurately measure the runtime of any function and retrieve the value in milliseconds. One convenient approach involves employing the defer feature.

In Go versions 1.x and earlier, you can define the following functions:

func trace(s string) (string, time.Time) {
    log.Println("START:", s)
    return s, time.Now()
}

func un(s string, startTime time.Time) {
    endTime := time.Now()
    log.Println("  END:", s, "ElapsedTime in seconds:", endTime.Sub(startTime))
}

Within your code, you can then call these functions as follows:

func someFunction() {
    defer un(trace("SOME_ARBITRARY_STRING_SO_YOU_CAN_KEEP_TRACK"))

    //do a bunch of stuff here...
}

By leveraging the defer statement, the trace() function is invoked at the start of the someFunction(), while the un() function is deferred to execute only after the completion of someFunction(). This approach provides accurate runtime logging while maintaining code simplicity.

Note that the provided code example uses logging statements, which may slightly affect the precision of the runtime measurements. If higher accuracy is crucial, consider experimenting with alternative techniques that minimize logging overhead.

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