more pkg and internal notes

README.md

@@ -41,13 +41,13 @@ See the [`/cmd`](cmd/README.md) directory for examples.
 
 ### `/internal`
 
-Private application and library code. This is the code you don't want others importing in their applications or libraries. Note that this layout pattern is enforced by the Go compiler itself. See the Go 1.4 [`release notes`](https://golang.org/doc/go1.4#internalpackages) for more details.
+Private application and library code. This is the code you don't want others importing in their applications or libraries. Note that this layout pattern is enforced by the Go compiler itself. See the Go 1.4 [`release notes`](https://golang.org/doc/go1.4#internalpackages) for more details. Note that you are not limited to the top level `internal` directory. You can have more than one `internal` directory at any level of your project tree.
 
 You can optionally add a bit of extra structure to your internal packages to separate your shared and non-shared internal code. It's not required (especially for smaller projects), but it's nice to have visual clues showing the intended package use. Your actual application code can go in the `/internal/app` directory (e.g., `/internal/app/myapp`) and the code shared by those apps in the `/internal/pkg` directory (e.g., `/internal/pkg/myprivlib`).
 
 ### `/pkg`
 
-Library code that's ok to use by external applications (e.g., `/pkg/mypubliclib`). Other projects will import these libraries expecting them to work, so think twice before you put something here :-)
+Library code that's ok to use by external applications (e.g., `/pkg/mypubliclib`). Other projects will import these libraries expecting them to work, so think twice before you put something here :-) Note that the `internal` directory is a better way to ensure your private packages are not importable because it's enforced by Go. The `/pkg` directory is still a good way to explicitly communicate that the code in that directory is safe for use by others.
 
 It's also a way to group Go code in one place when your root directory contains lots of non-Go components and directories making it easier to run various Go tools (as mentioned in these talks: [`Best Practices for Industrial Programming`](https://www.youtube.com/watch?v=PTE4VJIdHPg) from GopherCon EU 2018, [GopherCon 2018: Kat Zien - How Do You Structure Your Go Apps](https://www.youtube.com/watch?v=oL6JBUk6tj0) and [GoLab 2018 - Massimiliano Pippi - Project layout patterns in Go](https://www.youtube.com/watch?v=3gQa1LWwuzk)).
 

internal/README.md

@@ -1,6 +1,6 @@
 # `/internal`
 
-Private application and library code. This is the code you don't want others importing in their applications or libraries. Note that this layout pattern is enforced by the Go compiler itself. See the Go 1.4 [`release notes`](https://golang.org/doc/go1.4#internalpackages) for more details.
+Private application and library code. This is the code you don't want others importing in their applications or libraries. Note that this layout pattern is enforced by the Go compiler itself. See the Go 1.4 [`release notes`](https://golang.org/doc/go1.4#internalpackages) for more details. Note that you are not limited to the top level `internal` directory. You can have more than one `internal` directory at any level of your project tree.
 
 You can optionally add a bit of extra structure to your internal packages to separate your shared and non-shared internal code. It's not required (especially for smaller projects), but it's nice to have visual clues showing the intended package use. Your actual application code can go in the `/internal/app` directory (e.g., `/internal/app/myapp`) and the code shared by those apps in the `/internal/pkg` directory (e.g., `/internal/pkg/myprivlib`).
 

pkg/README.md

@@ -1,6 +1,6 @@
 # `/pkg`
 
-Library code that's ok to use by external applications (e.g., `/pkg/mypubliclib`). Other projects will import these libraries expecting them to work, so think twice before you put something here :-)
+Library code that's ok to use by external applications (e.g., `/pkg/mypubliclib`). Other projects will import these libraries expecting them to work, so think twice before you put something here :-) Note that the `internal` directory is a better way to ensure your private packages are not importable because it's enforced by Go. The `/pkg` directory is still a good way to explicitly communicate that the code in that directory is safe for use by others.
 
 It's also a way to group Go code in one place when your root directory contains lots of non-Go components and directories making it easier to run various Go tools (as mentioned in these talks: [`Best Practices for Industrial Programming`](https://www.youtube.com/watch?v=PTE4VJIdHPg) from GopherCon EU 2018, [GopherCon 2018: Kat Zien - How Do You Structure Your Go Apps](https://www.youtube.com/watch?v=oL6JBUk6tj0) and [GoLab 2018 - Massimiliano Pippi - Project layout patterns in Go](https://www.youtube.com/watch?v=3gQa1LWwuzk)).