diff --git a/content/guides/golang.md b/content/guides/golang.md
index 07476b0f5a0..2a39f00f33b 100644
--- a/content/guides/golang.md
+++ b/content/guides/golang.md
@@ -242,6 +242,12 @@ This `COPY` command uses a wildcard to copy all files with `.go` extension
 located in the current directory on the host (the directory where the `Dockerfile`
 is located) into the current directory inside the image.
 
+`COPY *.go ./` only matches `.go` files in that one directory. Packages
+under `pkg/` or other subdirectories are left out, so `go build` then
+fails to find them. For a multi-package module, copy the module root
+instead (`COPY . .`) and use a `.dockerignore` file to keep the context
+small.
+
 Now, to compile your application, use the familiar `RUN` command:
 
 ```dockerfile