Use "go install" instead of "go get" in README.md

See: https://go.dev/doc/go-get-install-deprecation
It's available since Go 1.16 and running "go get" recommends it in the future.
It the change is too new, maybe we can specify that "go get" should be used in older versions and "go install" in newer ones (since they allow you to specify a fixed version as well)

README.md

@@ -6,7 +6,7 @@ errcheck is a program for checking for unchecked errors in go programs.
 
 ## Install
 
-    go get -u github.com/kisielk/errcheck
+    go install github.com/kisielk/errcheck@latest
 
 errcheck requires Go 1.12 or newer, and depends on the package go/packages from the golang.org/x/tools repository.