Bump golang from 1.17-alpine to 1.18-alpine in /build (#50)

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Luca Comellini <[email protected]>

Author: dependabot[bot]

build/Dockerfile

@@ -8,7 +8,7 @@ COPY ${CONFIG_FILE} /etc/nginx-ns1-gslb/config.yaml
 ENTRYPOINT ["/nginx-ns1-gslb", "-config-file", "/etc/nginx-ns1-gslb/config.yaml"]
 
 
-FROM golang:1.17-alpine as builder
+FROM golang:1.18-alpine as builder
 WORKDIR /go/src/github.com/nginxinc/nginx-ns1-gslb/cmd/agent
 COPY go.mod go.sum /go/src/github.com/nginxinc/nginx-ns1-gslb/
 RUN go mod download