added Dockerfile for example server

v3/examples/server/Dockerfile

@@ -0,0 +1,51 @@
+# If it is more convenient for you to run an instrumented test server in a Docker
+# container, you can use this Dockerfile to build an image for that purpose.
+#
+# To build this image, have this Dockerfile in the current directory and run:
+#    docker build -t go-agent-test .
+#
+# To run a test, run the following:
+#    docker run -e NEW_RELIC_LICENSE_KEY="YOUR_KEY_HERE" -p 127.0.0.1:8000:8000 go-agent-test
+#    then drive traffic to it on localhost port 8000
+#
+#    This running application will write debugging logs showing all interaction
+#    with the collector on its standard output.
+#
+#    The following HTTP endpoints can be accessed on port 8000 to invoke different
+#    instrumented server features:
+#	/
+#	/add_attribute
+#	/add_span_attribute
+#	/async
+#	/background
+#	/background_log
+#	/browser
+#	/custom_event
+#	/custommetric
+#	/external
+#	/ignore
+#	/log
+#	/message
+#	/mysql
+#	/notice_error
+#	/notice_error_with_attributes
+#	/notice_expected_error
+#	/roundtripper
+#	/segments
+#	/set_name
+#	/version
+#
+FROM golang:1.22
+MAINTAINER Steve Willoughby <[email protected]>
+WORKDIR /go
+RUN git clone https://github.com/newrelic/go-agent
+WORKDIR /go/go-agent/v3
+RUN go mod tidy
+WORKDIR /go/go-agent/v3/examples/server
+RUN go mod tidy
+RUN go build
+EXPOSE 8000
+CMD ["/go/go-agent/v3/examples/server/server"]
+#
+# END
+#