diff --git a/go.md b/go.md
index 136e9d6..d3f6269 100755
--- a/go.md
+++ b/go.md
@@ -32,4 +32,21 @@ It's easy to understand and teaches you all you need to know.
 go get golang.org/x/tools/cmd/godoc
 ```
 
+# `go.mod`
+
+## `replace` [^go-mod-edit]
+
+```
+go mod edit -replace old.repo/location=../new/location
+```
+
+> The `-replace=old[@v]=new[@v]` flag adds a replacement of the given
+> module path and version pair. If the @v in old@v is omitted, a
+> replacement without a version on the left side is added, which applies
+> to all versions of the old module path. If the @v in new@v is omitted,
+> the new path should be a local module root directory, not a module
+> path. Note that -replace overrides any redundant replacements for old[@v],
+> so omitting @v will drop existing replacements for specific versions
+
 [^golang-godoc]: Andrew Gerrand, 31 March 2011 --- <https://blog.golang.org/godoc>
+[^go-mod-edit]: <https://golang.org/ref/mod#go-mod-edit>