staticcheck (#313)

* CI: use staticcheck for linting

This commit switches the linter for Go code from golint to staticcheck.
Golint has been deprecated since last year and staticcheck is a
recommended replacement.

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

* revendor

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

* cmd,pkg: fix lint warnings

Signed-off-by: Lucas Servén Marín <lserven@gmail.com>

vendor/honnef.co/go/tools/quickfix/doc.go

@@ -0,0 +1,147 @@
+// Package quickfix contains analyzes that implement code refactorings.
+// None of these analyzers produce diagnostics that have to be followed.
+// Most of the time, they only provide alternative ways of doing things,
+// requiring users to make informed decisions.
+//
+// None of these analyzes should fail a build, and they are likely useless in CI as a whole.
+package quickfix
+
+import "honnef.co/go/tools/analysis/lint"
+
+var Docs = lint.Markdownify(map[string]*lint.RawDocumentation{
+	"QF1001": {
+		Title:    "Apply De Morgan's law",
+		Since:    "2021.1",
+		Severity: lint.SeverityHint,
+	},
+
+	"QF1002": {
+		Title: "Convert untagged switch to tagged switch",
+		Text: `
+An untagged switch that compares a single variable against a series of
+values can be replaced with a tagged switch.`,
+		Before: `
+switch {
+case x == 1 || x == 2, x == 3:
+    ...
+case x == 4:
+    ...
+default:
+    ...
+}`,
+
+		After: `
+switch x {
+case 1, 2, 3:
+    ...
+case 4:
+    ...
+default:
+    ...
+}`,
+		Since:    "2021.1",
+		Severity: lint.SeverityHint,
+	},
+
+	"QF1003": {
+		Title: "Convert if/else-if chain to tagged switch",
+		Text: `
+A series of if/else-if checks comparing the same variable against
+values can be replaced with a tagged switch.`,
+		Before: `
+if x == 1 || x == 2 {
+    ...
+} else if x == 3 {
+    ...
+} else {
+    ...
+}`,
+
+		After: `
+switch x {
+case 1, 2:
+    ...
+case 3:
+    ...
+default:
+    ...
+}`,
+		Since:    "2021.1",
+		Severity: lint.SeverityInfo,
+	},
+
+	"QF1004": {
+		Title:    `Use \'strings.ReplaceAll\' instead of \'strings.Replace\' with \'n == -1\'`,
+		Since:    "2021.1",
+		Severity: lint.SeverityHint,
+	},
+
+	"QF1005": {
+		Title:    `Expand call to \'math.Pow\'`,
+		Text:     `Some uses of \'math.Pow\' can be simplified to basic multiplication.`,
+		Before:   `math.Pow(x, 2)`,
+		After:    `x * x`,
+		Since:    "2021.1",
+		Severity: lint.SeverityHint,
+	},
+
+	"QF1006": {
+		Title: `Lift \'if\'+\'break\' into loop condition`,
+		Before: `
+for {
+    if done {
+        break
+    }
+    ...
+}`,
+
+		After: `
+for !done {
+    ...
+}`,
+		Since:    "2021.1",
+		Severity: lint.SeverityHint,
+	},
+
+	"QF1007": {
+		Title: "Merge conditional assignment into variable declaration",
+		Before: `
+x := false
+if someCondition {
+    x = true
+}`,
+		After:    `x := someCondition`,
+		Since:    "2021.1",
+		Severity: lint.SeverityHint,
+	},
+
+	"QF1008": {
+		Title:    "Omit embedded fields from selector expression",
+		Since:    "2021.1",
+		Severity: lint.SeverityHint,
+	},
+
+	"QF1009": {
+		Title:    `Use \'time.Time.Equal\' instead of \'==\' operator`,
+		Since:    "2021.1",
+		Severity: lint.SeverityInfo,
+	},
+
+	"QF1010": {
+		Title:    "Convert slice of bytes to string when printing it",
+		Since:    "2021.1",
+		Severity: lint.SeverityHint,
+	},
+
+	"QF1011": {
+		Title:    "Omit redundant type from variable declaration",
+		Since:    "2021.1",
+		Severity: lint.SeverityHint,
+	},
+
+	"QF1012": {
+		Title:    `Use \'fmt.Fprintf(x, ...)\' instead of \'x.Write(fmt.Sprintf(...))\'`,
+		Since:    "2022.1",
+		Severity: lint.SeverityHint,
+	},
+})