The comma, ok Pattern

While studying the Go-language, we encountered several times the so-called comma, ok idiom where an expression returns two values: the first of which is a value or nil, and the second is true/false or an error. An if-condition with initialization and then testing on the second-value leads to succinct and elegant code. This is a significant pattern in idiomatic Go-code. Here are all cases summarized:

Testing for errors on function return

var value Type_value
var err error
if value, err = pack1.Func1(param1); err != nil {
 

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