chore: add docker-based dev env

Dockerfile

@@ -1,14 +1,23 @@
-FROM golang:1.18.3-alpine3.16
+FROM golang:1.18.3-alpine3.16 AS base
 
 ENV APP_ROOT /opt/sfu
-
-RUN mkdir -p "$APP_ROOT"
+ARG gid=1000
+ARG uid=1000
+RUN mkdir -p "$APP_ROOT" \
+    && addgroup --system sfu -g $gid \
+    && adduser -h "$APP_ROOT" --disabled-password --system -u $uid --ingroup sfu sfu
 WORKDIR "$APP_ROOT"
+USER sfu:sfu
 
+FROM base AS build
 COPY go.mod .
 COPY main.go .
 COPY logger.go .
-
 RUN go build \
     && rm -r go.mod *.go
-ENTRYPOINT [ "/bin/sh", "-c", "$APP_ROOT/main"]
+
+FROM build AS run_prod
+ENTRYPOINT [ "/bin/sh", "-c", "$APP_ROOT/main"]
+
+FROM base AS run_dev
+ENTRYPOINT [ "/usr/local/go/bin/go", "run", "." ]