all: update install commands to go install pkg@version

Updates golang/go#43684
Updates golang/go#49101

Change-Id: I2f0c7920bcd6ce0429f1b7bdda3747bf376775f2
Reviewed-on: https://go-review.googlesource.com/c/tools/+/357714
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
Trust: Rebecca Stambler <rstambler@golang.org>
Trust: Peter Weinberger <pjw@google.com>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
diff --git a/README.md b/README.md
index 789747b..71a945a 100644
--- a/README.md
+++ b/README.md
@@ -9,15 +9,14 @@
 distributions.
 
 Others, including the Go `guru` and the test coverage tool, can be fetched with
-`go get`.
+`go install`.
 
 Packages include a type-checker for Go and an implementation of the
 Static Single Assignment form (SSA) representation for Go programs.
 
 ## Download/Install
 
-The easiest way to install is to run `go get -u golang.org/x/tools/...`. You can
-also manually git clone the repository to `$GOPATH/src/golang.org/x/tools`.
+The easiest way to install is to run `go install golang.org/x/tools/...@latest`.
 
 ## JS/CSS Formatting
 
diff --git a/gopls/doc/advanced.md b/gopls/doc/advanced.md
index 1891f1f..d8e47f7 100644
--- a/gopls/doc/advanced.md
+++ b/gopls/doc/advanced.md
@@ -9,7 +9,7 @@
 version), run:
 
 ```sh
-GO111MODULE=on go get golang.org/x/tools/gopls@vX.Y.Z
+GO111MODULE=on go install golang.org/x/tools/gopls@vX.Y.Z
 ```
 
 Where `vX.Y.Z` is the desired version.
@@ -56,7 +56,7 @@
 `golang.org/dl/gotip`:
 
 ```
-$ go get golang.org/dl/gotip
+$ go install golang.org/dl/gotip@latest
 $ gotip download
 ```
 
diff --git a/internal/lsp/general.go b/internal/lsp/general.go
index 44715f0..a946c80 100644
--- a/internal/lsp/general.go
+++ b/internal/lsp/general.go
@@ -103,7 +103,7 @@
 		if dep.Path == "github.com/sergi/go-diff" && dep.Version == "v1.2.0" {
 			if err := s.eventuallyShowMessage(ctx, &protocol.ShowMessageParams{
 				Message: `It looks like you have a bad gopls installation.
-Please reinstall gopls by running 'GO111MODULE=on go get golang.org/x/tools/gopls@latest'.
+Please reinstall gopls by running 'GO111MODULE=on go install golang.org/x/tools/gopls@latest'.
 See https://github.com/golang/go/issues/45732 for more information.`,
 				Type: protocol.Error,
 			}); err != nil {