Please, change var iconUrl to "http://openweathermap.org/img/wn/%s"

[dnegorov]

openweathermap/openweathermap.go

Line 33 in 73cba80

iconURL = "http://openweathermap.org/img/w/%s"

On the page https://openweathermap.org/weather-conditions recomended to use URL like http://openweathermap.org/img/wn/50d@4x.png
With this URL you can get image with different sizes by adding postfix "@nx" to file name, where N can be 2 or 4:
"50d.png" - defaul size 50x50px,
"50d@2x.png" - x2 size 100x100px,
"50d@4x.png" - x4 size 200x200px.

Example:
owm.RetrieveIcon(".", w.Weather[0].Icon+"@4x.png")

And change var iconUrl to var IconUrl to make it changeable. In this case users can change URL to different icon set.