NOAA astrological algorithms for sunrise and sunset ported to Go

• func CalcSunrise(t time.Time, latitude float64, longitude float64) time.Time calculates the sunrise, in local time, on the day t at the location specified in longitude and latitude.
• func NextSunrise(tAfter time.Time, latitude float64, longitude float64) (tSunrise time.Time) returns date/time of the next sunrise after tAfter
• func CalcSunset(t time.Time, latitude float64, longitude float64) time.Time calculates the sunset, in local time, on the day t at the location specified in longitude and latitude.
• func NextSunset(tAfter time.Time, latitude float64, longitude float64) (tSunset time.Time) returns date/time of the next sunset after tAfter

• func CalcDawn(t time.Time, latitude float64, longitude float64, solarElevation float64) time.Time calculates Dawn or Sunrise (depending on solarElevation given), in local time, on the day t at the location specified in longitude and latitude.
• func CalcDusk(t time.Time, latitude float64, longitude float64, solarElevation float64) time.Time calculates Dusk or Sunset (depending on solarElevation given), in local time, on the day t at the location specified in longitude and latitude.
• func NextDawn(tAfter time.Time, latitude float64, longitude float64, solarElevation float64) (tSunrise time.Time) returns date/time of the specified solarElevation before Sunrise after tAfter
• func NextDusk(tAfter time.Time, latitude float64, longitude float64, solarElevation float64) (tSunrise time.Time) returns date/time of the specified solarElevation after Sunset after tAfter.

• ASTRONOMICAL_DAWN
• `ASTRONOMICAL_DUSK´
• NAUTICAL_DAWN
• NAUTICAL_DUSK
• CIVIL_DAWN
• CIVIL_DUSK
• SUNRISE
• SUNSET
• GOLDEN_HOUR

go get -u github.com/btittelbach/astrotime

package main

import (
        "astrotime"
        "fmt"
        "time"
)

const LATITUDE = float64(38.8895)
const LONGITUDE = float64(77.0352)

func main() {
        t := astrotime.NextSunrise(time.Now(), LATITUDE, LONGITUDE)

        tzname, _ := t.Zone()
        fmt.Printf("The next sunrise at the Washington Monument is %d:%02d %s on %d/%d/%d.\n", t.Hour(), t.Minute(), tzname, t.Month(), t.Day(), t.Year())
}