coordconv is a manual port of the Geotrans 3.7 MGRS conversion code from C++ to Go. It also makes public the UTM and UPS converters as well as the underlying transverse mercator and polar stereographic projections.
It has been tested with 4million+ points uniformly spread across the globe and returns identical results to the standard Geotrans library. The unit tests included contain an abbreviated test table at testdata/geotrans.log with 40,000 points which was generated with the included geotrans_table_cpp. It can be modified and used to regenerate the included geotrans.log, or a more comprehensive one if desired.
Constructors are provided so you can use custom ellipsoid parameters, but defaults are provided for WGS84:
mgrs, _ := coordconv.DefaultMGRSConverter.ConvertFromGeodetic(s2.LatLngFromDegrees(0, 0), 5)
fmt.Println(mgrs) // 31NAA6602100000
geo, _ := coordconv.DefaultMGRSConverter.ConvertToGeodetic("16SGC3855124838")
fmt.Println(geo) // [33.6366624, -84.4280571]The geotrans code is public domain, so in spirit this is public domain as well. I only made minor changes along the way to make it behave a bit more like like standard Go code (e.g. returning an error when the C++ code threw an exception)