chore: remove run-in-docker logic from Makefile

The same benefits can be achieved by simply launching an
interactive docker session inside a supported image and running
commands from there. This approach has some additional benefits
- Easier to maintain
- Debloats Makefile
- Less hidden magic
- Same code for local and containerised execution

Makefile

@@ -11,15 +11,8 @@ else
 OSFAMILY=linux
 endif
 
-ifeq ($(USE_GO_CONTAINERS),)
 GO=go
 GOFMT=gofmt
-else
-UID:=$(shell id -u)
-DOCKER_OPTS=--rm -u $(UID) -v $(HOME):$(HOME) -e HOME -e USER=$(USER) -e USERNAME=$(USER) -w $(PWD)
-GO=docker run $(DOCKER_OPTS) -e GOARCH -e GOOS -e CGO_ENABLED golang:$(GO-VERSION) go
-GOFMT=docker run $(DOCKER_OPTS) -e GOARCH -e GOOS -e CGO_ENABLED golang:$(GO-VERSION) gofmt
-endif
 
 SRC = $(shell find . -name "*.go" | grep -v "_test\." )
 

README.md

@@ -64,7 +64,13 @@ It supports the following sub-commands:
 ## Development
 
 `make` is used to orchestrate most development tasks. 
-`go` is required to build the broker. If you don't have `go` installed, it is possible to use a `docker` image to build and unit test the broker. If the environment variable `USE_GO_CONTAINERS` exists, `make` will use `docker` versions of the tools so you don't need to have them installed locally. 
+`go` is required to build the broker.
+If you don't have `go` installed, it is possible to use `docker` to launch an interactive shell into some supported image containing all necessary tools. For example:
+```
+# From the root of this repo run:
+docker run -it --rm -v "${PWD}:/repo" --workdir "/repo" --entrypoint "/bin/bash" cflondonservices/csb-ci-main
+make
+```
 
 There are make targets for most common dev tasks. Running make without a target will list the possible targets.