cmd/go: add mod edit -toolchain and work edit -toolchain

We have added a new toolchain directive in go.mod and go.work.
This CL adds support in mod edit and work edit for changing the toolchain line.

For #57001.

Change-Id: I36a960796630a359b8a587877cb9548c299d5c87
Reviewed-on: https://go-review.googlesource.com/c/go/+/497296
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: Russ Cox <rsc@golang.org>

1 files changed, 15 insertions, 9 deletions

diff --git a/src/cmd/go/alldocs.go b/src/cmd/go/alldocs.go
index 455a0f75363..6a1cb8b8103 100644
--- a/src/cmd/go/alldocs.go
+++ b/src/cmd/go/alldocs.go
@@ -1210,6 +1210,8 @@
 //
 // The -go=version flag sets the expected Go language version.
 //
+// The -toolchain=name flag sets the Go toolchain to use.
+//
 // The -print flag prints the final go.mod in its text format instead of
 // writing it back to go.mod.
 //
@@ -1222,12 +1224,13 @@
 //	}
 //
 //	type GoMod struct {
-//		Module  ModPath
-//		Go      string
-//		Require []Require
-//		Exclude []Module
-//		Replace []Replace
-//		Retract []Retract
+//		Module    ModPath
+//		Go        string
+//		Toolchain string
+//		Require   []Require
+//		Exclude   []Module
+//		Replace   []Replace
+//		Retract   []Retract
 //	}
 //
 //	type ModPath struct {
@@ -1523,6 +1526,8 @@
 //
 // The -go=version flag sets the expected Go language version.
 //
+// The -toolchain=name flag sets the Go toolchain to use.
+//
 // The -print flag prints the final go.work in its text format instead of
 // writing it back to go.mod.
 //
@@ -1530,9 +1535,10 @@
 // writing it back to go.mod. The JSON output corresponds to these Go types:
 //
 //	type GoWork struct {
-//		Go      string
-//		Use     []Use
-//		Replace []Replace
+//		Go        string
+//		Toolchain string
+//		Use       []Use
+//		Replace   []Replace
 //	}
 //
 //	type Use struct {