cmd/go: make hints in error messages more consistent

* All commands the user can run to fix the problem now appear alone on
  a separate line after a tab.
* Removed -d from 'go get' commands.
* Replaced 'go mod tidy' with 'go mod download $modpath' when a
  package might be provided by a module missing a sum.
* Errors about 'path@version' syntax are more explicit.

Fixes #29415
Fixes #42087
Fixes #43430
Fixes #43523

Change-Id: I4427c2c4506a727a2c727d652fd2d506bb134d3b
Reviewed-on: https://go-review.googlesource.com/c/go/+/282121
Trust: Jay Conrod <jayconrod@google.com>
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/cmd/go/internal/modload/load.go b/src/cmd/go/internal/modload/load.go
index ae5b8ef6ab..cd36da6a87 100644
--- a/src/cmd/go/internal/modload/load.go
+++ b/src/cmd/go/internal/modload/load.go
@@ -868,7 +868,7 @@ func loadFromRoots(params loaderParams) *loader {
 						// base.Errorf. Ideally, 'go list' should not fail because of this,
 						// but today, LoadPackages calls WriteGoMod unconditionally, which
 						// would fail with a less clear message.
-						base.Errorf("go: %[1]s: package %[2]s imported from implicitly required module; try 'go get -d %[1]s' to add missing requirements", pkg.path, dep.path)
+						base.Errorf("go: %[1]s: package %[2]s imported from implicitly required module; to add missing requirements, run:\n\tgo get %[2]s@%[3]s", pkg.path, dep.path, dep.mod.Version)
 					}
 					ld.direct[dep.mod.Path] = true
 				}