GODRIVER-416: run errcheck in evergreen and fix outstanding errors

Change-Id: I1420c05e17a20018c71cab2f4ae7c2e3a6c66e79

Author: Sam Kleinman

.evergreen/config.yml

@@ -120,6 +120,7 @@ functions:
            ${PREPARE_SHELL}
            # any go tools that we need
            go get -u github.com/golang/lint/golint
+           go get -u github.com/kisielk/errcheck
 
            # initialize submodules
            git submodule init
@@ -211,17 +212,9 @@ functions:
           done
 
 
-  install-dependencies:
-    type: test
-    params:
-      working_dir: src/github.com/mongodb/mongo-go-driver
-      script: |
-        ${PREPARE_SHELL}
-        file="${PROJECT_DIRECTORY}/.evergreen/install-dependencies.sh"
-        [ -f ${file} ] && sh ${file} || echo "${file} not available, skipping"
-
   run-make:
     - command: shell.exec
+      type: test
       params:
         working_dir: src/github.com/mongodb/mongo-go-driver
         script: |
@@ -292,7 +285,6 @@ pre:
   - func: windows-fix
   - func: fix-absolute-paths
   - func: make-files-executable
-  - func: install-dependencies
 
 post:
   - command: gotest.parse_files
@@ -309,6 +301,13 @@ tasks:
           vars:
             targets: check-fmt
 
+    - name: sa-errcheck
+      tags: ["static-analysis"]
+      commands:
+        - func: run-make
+          vars:
+            targets: errcheck
+
     - name: sa-lint
       tags: ["static-analysis"]
       commands:

bson/extjson_builder.go

@@ -43,8 +43,7 @@ func ParseExtJSONArray(s string) (*Array, error) {
 	}
 
 	buf := make([]byte, b.RequiredBytes())
-	_, err = b.WriteDocument(buf)
-	if err != nil {
+	if _, err = b.WriteDocument(buf); err != nil {
 		return nil, err
 	}