fix(pkg/stash): close etcd sessions (#1887)

.golangci.yml

@@ -6,6 +6,10 @@ linters-settings:
   cyclop:
     max-complexity: 12
     skip-tests: true
+  errcheck:
+    exclude-functions:
+      - (*go.etcd.io/etcd/client/v3/concurrency.Mutex).Unlock
+      - (*go.etcd.io/etcd/client/v3/concurrency.Session).Close
   gofumpt:
     extra-rules: true
 
@@ -50,15 +54,15 @@ linters:
 issues:
   exclude-use-default: false
   exclude:
-    - 'package-comments: should have a package comment'
-    - 'ST1000: at least one file in a package should have a package comment'
-    - 'G204: Subprocess launched with a potential tainted input or cmd arguments'
-    - 'G204: Subprocess launched with variable'
-    - 'G402: TLS MinVersion too low.'
-    - 'const `op` is unused'
+    - "package-comments: should have a package comment"
+    - "ST1000: at least one file in a package should have a package comment"
+    - "G204: Subprocess launched with a potential tainted input or cmd arguments"
+    - "G204: Subprocess launched with variable"
+    - "G402: TLS MinVersion too low."
+    - "const `op` is unused"
   exclude-rules:
     - path: cmd/proxy/main.go
-      text: 'G108: Profiling endpoint is automatically exposed on /debug/pprof'
+      text: "G108: Profiling endpoint is automatically exposed on /debug/pprof"
     - path: pkg/stash/stasher.go
       linters:
         - contextcheck