diff --git a/Development/Go/Modules.md b/Development/Go/Modules.md
index 7879ec6..af95a14 100644
--- a/Development/Go/Modules.md
+++ b/Development/Go/Modules.md
@@ -22,30 +22,12 @@ go mod tidy
 go mod vendor
 ```
 
-Outside modules:
-
-```sh
-GOMODULE11=on go get example.com/foo/bar
-```
-
 Update go version:
 
 ```sh
 go mod edit -go=1.XY
 ```
 
-Replace module path and version pair:
-
-```sh
-go mod edit -replace old[@v]=new[@v]
-```
-
-Drop replace module path:
-
-```sh
-go mod edit -dropreplace old[@v]
-```
-
 In world of corporation, we work with private repository, add to `~/.bashrc`, `~/.zshrc`:
 
 ```sh
diff --git a/Development/Go/errors.md b/Development/Go/errors.md
index 8b8a72a..a5517c7 100644
--- a/Development/Go/errors.md
+++ b/Development/Go/errors.md
@@ -11,3 +11,13 @@ Unwrap error:
 ```go
 rootErr := errors.Unwrap(err)
 ```
+
+Compare error:
+
+```go
+// Don't
+if err == CustomErr
+
+// Do
+if errors.Is(err, CustomErr)
+```