Update Dockerfile

Dockerfile

@@ -31,7 +31,12 @@ RUN case ${TARGETPLATFORM} in \
     apt-get clean && \
     apt-get autoremove -y && \
     curl -LO https://github.com/ginuerzh/gost/releases/download/v${GOST_VERSION}/gost-linux-${ARCH}-${GOST_VERSION}.gz && \
-    gunzip gost-linux-${ARCH}-${GOST_VERSION}.gz && \
+    if file gost-linux-${ARCH}-${GOST_VERSION}.gz | grep -q 'gzip compressed data'; then \
+      gunzip gost-linux-${ARCH}-${GOST_VERSION}.gz; \
+    else \
+      echo "Downloaded file is not a valid gzip file"; \
+      exit 1; \
+    fi && \
     mv gost-linux-${ARCH}-${GOST_VERSION} /usr/bin/gost && \
     chmod +x /usr/bin/gost && \
     chmod +x /entrypoint.sh && \
@@ -51,4 +56,4 @@ ENV WARP_SLEEP=2
 HEALTHCHECK --interval=15s --timeout=5s --start-period=10s --retries=3 \
   CMD /healthcheck/index.sh
 
-ENTRYPOINT ["/entrypoint.sh"]
+ENTRYPOINT ["/entrypoint.sh"]