參考： https://golangcode.com/checking-if-date-has-been-set/
https://stackoverflow.com/questions/20924303/date-time-comparison-in-golang
// utc life loc, _ := time.LoadLocation("UTC") // setup a start and end time createdAt := time.Now().In(loc).Add(1 * time.Hour) expiresAt := time.Now().In(loc).Add(4 * time.Hour) // get the diff diff := expiresAt.Sub(createdAt) fmt.Printf("Lifespan is %+v", diff)
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Check If a Date/Time Has Been Set with IsZero
In Go, we can store and use dates using the time package and although a date in Go cannot be saved as null (because there’s no such thing) there is an unset state. This unset state can be shown as 0001-01-01 00:00:00 +0000 UTC and there’s a simple way we can check if a date variable has been populated, as demonstrated below. It’s also important to note that these are not unix timestamps, which go back as far as 1970, but can handle a large spectrum of dates.
package main import ( "fmt" "time" ) func main() { var myDate time.Time // IsZero returns a bool of whether a date has been set, but as the printf shows it will // still print a zero-based date if it hasn't been set. if myDate.IsZero() { fmt.Printf("No date has been set, %s\n", myDate) } // Demonstrating that by setting a date, IsZero now returns false myDate = time.Date(2019, time.February, 1, 0, 0, 0, 0, time.UTC) if !myDate.IsZero() { fmt.Printf("A date has been set, %s\n", myDate) } } 
Use the time package to work with time information in Go.
Time instants can be compared using the Before, After, and Equal methods. The Sub method subtracts two instants, producing a Duration. The Add method adds a Time and a Duration, producing a Time.
Play example:
package main import ( "fmt" "time" ) func inTimeSpan(start, end, check time.Time) bool { return check.After(start) && check.Before(end) } func main() { start, _ := time.Parse(time.RFC822, "01 Jan 15 10:00 UTC") end, _ := time.Parse(time.RFC822, "01 Jan 16 10:00 UTC") in, _ := time.Parse(time.RFC822, "01 Jan 15 20:00 UTC") out, _ := time.Parse(time.RFC822, "01 Jan 17 10:00 UTC") if inTimeSpan(start, end, in) { fmt.Println(in, "is between", start, "and", end, ".") } if !inTimeSpan(start, end, out) { fmt.Println(out, "is not between", start, "and", end, ".") } }