In certain parts of the U.S., particularly the South, we often call other guys "son". It's a colloquialism, I suppose, and used in an atmosphere of friendship.
Country music legend Jerry Reed, for one, called everybody "son".
Same here in Eastern Canada, especially Cape Breton, "son" and/or "buddy" are used almost interchangeably and are meant as friendly greetings.
Well, Don, old son, old buddy...it is a snowy, windy and relatively balmy -24 Celsius here today (-11 for you Fahrenheit chaps)...a day on the golf course here would require big gloves, warm clothes, insulated (or heated) club handles and orange balls.

Fore!

Ian