Fix examples; Document chi v3.x -> chi v4 upgrade steps

.travis.yml

@@ -5,11 +5,12 @@ go:
   - 1.11.x
 
 script:
-  - GO111MODULE=on go test ./...
+  - export GO111MODULE=on
+  - go test ./...
+  - for i in _examples/*/; do go build $i/*.go || exit 1; done
   - >
     go_version=$(go version);
     if [ ${go_version:13:4} = "1.11" ]; then
       go get -u golang.org/x/tools/cmd/goimports;
       goimports -d -e ./ | grep '.*' && { echo; echo "Aborting due to non-empty goimports output."; exit 1; } || :;
     fi
-  - cd _examples && for i in */; do GO111MODULE=on go build $i/*.go; done

CHANGELOG.md

@@ -5,6 +5,16 @@
 - chi v4 requires Go 1.10.3+ (or Go 1.9.7+)
 - chi v4 is a Go module and thus breaks the import path; use `github.com/go-chi/chi/v4` and `github.com/go-chi/chi/v4/middleware`
 
+### Upgrading your codebase from chi v3.x to chi v4
+
+Example using GNU find (`brew install find`):
+```
+$ find . -type f -name '*.go' -not -path "./vendor/*" -exec sed -i 's+github.com/go-chi/chi+github.com/go-chi/chi/v4+g' {} \;
+```
+
+We recommend vendoring the dependencies via `GO111MODULE=on go mod vendor && GO111MODULE=on go mod tidy`.
+
+If your repository still pulls in the old import path, you can figure out why by running `GO111MODULE=on go mod why github.com/go-chi/chi`.
 
 ## v3.3.4 (2019-01-07)
 

chi.go

@@ -1,7 +1,7 @@
 //
 // Package chi is a small, idiomatic and composable router for building HTTP services.
 //
-// chi requires Go 1.7 or newer.
+// chi v4 requires Go 1.10.3+ (or Go 1.9.7+).
 //
 // Example:
 //  package main
@@ -25,7 +25,7 @@
 //  	http.ListenAndServe(":3333", r)
 //  }
 //
-// See github.com/go-chi/chi/v4/_examples/ for more in-depth examples.
+// See https://github.com/go-chi/chi/tree/master/_examples for more in-depth examples.
 //
 // URL patterns allow for easy matching of path components in HTTP
 // requests. The matching components can then be accessed using