The only requirement is the Go Programming Language, at least v1.7.
$ go get -u github.com/kataras/iris/iris
this will update the dependencies also.
If you are connected to the internet through China, according to this, you might have problems installing Iris.
Follow the below steps:
$ go get github.com/kataras/iris/iriswithout -u
If you have any problems installing Iris, just delete the directory
$GOPATH/src/github.com/kataras/iris, open your shell and run
go get -u github.com/kataras/iris/iris.