Update to Go 1.15.7 (#138)

diff --git a/CHANGES.md b/CHANGES.md
index e2f3ab5..87d8276 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -17,7 +17,7 @@
 #
 -->
 # (next release)
-- go 1.15 runtime upgraded to 1.15.5
+- go 1.15 runtime upgraded to 1.15.7
 - go 1.13 runtime upgraded to 1.13.15
 - add 'apt-get upgrade' to the image build of go 1.15 and go 1.13 to get latest security fixes during each build, for the case the base images are not updated frequently
 
@@ -29,7 +29,6 @@
 - added OW_WAIT_FOR_ACK such at if true, the proxy waits for an acknowledgement from the action on startup
 - added OW_EXECUTION_ENV to validate the execution environment before starting an action
 - write compilation logs to standard out
-
 # 1.15.0
 - added OW_ACTION_VERSION to action environment (PR#113)
 - propagate API_HOST from parent to child process (PR#115)
diff --git a/golang1.15/Dockerfile b/golang1.15/Dockerfile
index c60eb17..04ab74c 100644
--- a/golang1.15/Dockerfile
+++ b/golang1.15/Dockerfile
@@ -14,7 +14,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 #
-FROM golang:1.15.5
+FROM golang:1.15.7
 RUN echo "deb http://deb.debian.org/debian buster-backports main contrib non-free" \
      >>/etc/apt/sources.list &&\
     echo 'debconf debconf/frontend select Noninteractive' | debconf-set-selections &&\