Generics in Go
As someone who properly learned to program using Java and still works with Java almost every day, I am used to generics. Flexible parameters whose constraints do not yet have to be set during definition. The fact that there are no generics in Go took some getting used to.
But it seems that could change in the not too distant future. After years of discussions, the Go team has created a proposal that introduces generics into Go. With Go 1.18 it could be finally implemented.
More info in the proposal and blog entry.