chore(deps): bump golang from 1.20 to 1.21 (#9)

Bumps golang from 1.20 to 1.21.

---
updated-dependencies:
- dependency-name: golang
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Dockerfile

@@ -1,5 +1,5 @@
 # build
-FROM golang:1.20 as builder
+FROM golang:1.21 as builder
 WORKDIR         /go/src/sshportal
 COPY            . ./
 RUN             go build -ldflags="-X main.GitSha=$(git rev-parse --short HEAD) -X main.GitTag=$(git describe --tags --always) -extldflags '-static' -w -s" -tags osusergo,netgo,sqlite_omit_load_extension -v -o /go/bin/sshportal