Split the relay-client binary into a binary and library. (#200)

This simplifies testing in the future.

src/go/cmd/http-relay-client/BUILD.bazel

@@ -1,15 +1,16 @@
-package(default_visibility = ["//visibility:public"])
-
-load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_library", "go_test")
+load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_library")
 load("@rules_oci//oci:defs.bzl", "oci_image")
 load("@rules_pkg//pkg:tar.bzl", "pkg_tar")
 
+package(default_visibility = ["//visibility:public"])
+
 go_library(
     name = "go_default_library",
     srcs = ["main.go"],
     importpath = "github.com/googlecloudrobotics/core/src/go/cmd/http-relay-client",
     visibility = ["//visibility:private"],
     deps = [
+        "//src/go/cmd/http-relay-client/client:go_default_library",
         "//src/proto/http-relay:go_default_library",
         "@com_github_cenkalti_backoff//:go_default_library",
         "@io_opencensus_go//plugin/ochttp:go_default_library",
@@ -24,20 +25,6 @@ go_library(
     ],
 )
 
-go_test(
-    name = "go_default_test",
-    size = "small",
-    srcs = ["main_test.go"],
-    embed = [":go_default_library"],
-    visibility = ["//visibility:private"],
-    deps = [
-        "//src/proto/http-relay:go_default_library",
-        "@com_github_onsi_gomega//:go_default_library",
-        "@in_gopkg_h2non_gock_v1//:go_default_library",
-        "@org_golang_google_protobuf//proto:go_default_library",
-    ],
-)
-
 go_binary(
     name = "http-relay-client-app",
     embed = [":go_default_library"],

src/go/cmd/http-relay-client/client/BUILD.bazel

@@ -0,0 +1,36 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+
+package(default_visibility = ["//visibility:public"])
+
+go_library(
+    name = "go_default_library",
+    srcs = ["client.go"],
+    importpath = "github.com/googlecloudrobotics/core/src/go/cmd/http-relay-client/client",
+    deps = [
+        "//src/proto/http-relay:go_default_library",
+        "@com_github_cenkalti_backoff//:go_default_library",
+        "@io_opencensus_go//plugin/ochttp:go_default_library",
+        "@io_opencensus_go//plugin/ochttp/propagation/tracecontext:go_default_library",
+        "@io_opencensus_go//trace:go_default_library",
+        "@io_opencensus_go_contrib_exporter_stackdriver//:go_default_library",
+        "@org_golang_google_protobuf//proto:go_default_library",
+        "@org_golang_x_net//context:go_default_library",
+        "@org_golang_x_net//http2:go_default_library",
+        "@org_golang_x_oauth2//:go_default_library",
+        "@org_golang_x_oauth2//google:go_default_library",
+    ],
+)
+
+go_test(
+    name = "go_default_test",
+    size = "small",
+    srcs = ["client_test.go"],
+    embed = [":go_default_library"],
+    visibility = ["//visibility:private"],
+    deps = [
+        "//src/proto/http-relay:go_default_library",
+        "@com_github_onsi_gomega//:go_default_library",
+        "@in_gopkg_h2non_gock_v1//:go_default_library",
+        "@org_golang_google_protobuf//proto:go_default_library",
+    ],
+)