bcicen/go-units

package main

import (
	"fmt"
	u "github.com/bcicen/go-units"
)

func main() {
	// convert a simple float from celsius to fahrenheit
	fmt.Println(u.MustConvertFloat(25.5, u.Celsius, u.Fahrenheit)) // outputs "77.9 fahrenheit"

	// convert a units.Value instance
	val := u.NewValue(25.5, u.Celsius)

	fmt.Println(val)                           // "25.5 celsius"
	fmt.Println(val.MustConvert(u.Fahrenheit)) // "77.9 fahrenheit"
	fmt.Println(val.MustConvert(u.Kelvin))     // "298.65 kelvin"
}

val := u.NewValue(2.0, u.Nibble)
fmt.Println(val)                     // "2 nibbles"
fmt.Println(val.MustConvert(u.Byte)) // "1 byte"

// value formatting options may also be specified:
opts := u.FmtOptions{
  Label:     true, // append unit name/symbol
  Short:     true, // use unit symbol
  Precision: 3,
}

val = u.NewValue(15.456932, u.KiloMeter)
fmt.Println(val)           // "15.456932 kilometers"
fmt.Println(val.Fmt(opts)) // "15.457 km"
fmt.Println(val.Float())   // "15.456932"

// symbol
unit, err := u.Find("m")
// name
unit, err := u.Find("meter")
// alternate spelling
unit, err := u.Find("metre")

// register custom unit names
Ding := u.NewUnit("ding", "di")
Dong := u.NewUnit("dong", "do")

// there are 100 dongs in a ding
u.NewRatioConversion(Ding, Dong, 100.0)

val := u.NewValue(25.0, Ding)

fmt.Printf("%s = %s\n", val, val.MustConvert(Dong)) // "25 dings = 2500 dongs"

// conversions are automatically registered when using magnitude prefix helper methods
KiloDong := u.Kilo(Dong)
fmt.Println(u.MustConvertFloat(1000.0, Dong, KiloDong)) // "1 kilodong"