Added CODE_CONVENTIONS.md and linters to enforce it, and applied it across the codebase

CODE_CONVENTIONS.md sets out the conventions for Go code in this
repository: naming, layout, comments, errors, logging, configuration and
tests. .golangci.json enables the linters that check the parts that can be
checked (each limited to the rules the conventions use); the rest is
applied by hand.

Applied across the codebase:
- Naming: full-word names in application code, initialisms in one case
  (BuyerID, PrintJSON, PrintYAML, ocdsGetBuyerID), no names shadowing
  built-ins (min/max are minGap/maxGap), mustRaw renamed rawJSON as it
  returns nil rather than panicking, and config.ConfigLevelToLogLevel
  renamed LevelToLogLevel.
- Layout: lines kept to 80 characters where possible, assignments taken
  out of if and for statements that don't fit, wrapped arguments all on
  one line or one per line, steps separated by blank lines, no else after
  a return, function and struct literals wrapped.
- Comments: doc comments on every exported name (including each section's
  Map, Flatten, TypeOf, ValueOf and SetValue), section banners, British
  spelling.
- Errors: a created error starts with its package name, a wrapping error
  adds only what was being done, sentinels in one commented var block,
  errors.Is and errors.As in place of == and type assertions, and no
  err := shadowing of a named result. That fixes the mock server losing
  its access log's close error.
- Logging: the fetcher passes its workers an untagged logger, so
  findatender's lines are tagged with their own component rather than
  with fetcher's as well; cmd/mock-fts logs "stopped" with slog.
- Configuration: util.WithTimeout (moved from the websocket package)
  applies a timeout of 0 or less as no limit, used for the websocket
  write and ping, TCP close and tcpserver shutdown timeouts; every setting
  documents what 0 or empty means, including the rate limit rule's keys
  in internal/config/README.md.
- Tests: related tests merged into table-driven ones with named cases.

Separately from CODE_CONVENTIONS.md, internal/store/README.md gains a soft
SQL style convention for the queries in internal/store/queries.go, and the
queries are reformatted to follow it.

internal/cli/fetch/command.go

@@ -8,7 +8,8 @@ import (
 	"git.avsdev.uk/Go/job-search/internal/cli"
 )
 
-// NewCommand returns the "fetch" command, which fetches opportunities once or as a service.
+// NewCommand returns the "fetch" command, which fetches opportunities once or
+// as a service.
 func NewCommand(opts *cli.Options) *cobra.Command {
 	cmd := &cobra.Command{
 		Use:   "fetch",
@@ -22,5 +23,6 @@ func NewCommand(opts *cli.Options) *cobra.Command {
 	}
 	cmd.AddCommand(commandOnce(opts))
 	cmd.AddCommand(commandService(opts))
+
 	return cmd
 }

internal/cli/fetch/once.go

@@ -29,7 +29,9 @@ var stageTags = map[string][]string{
 
 // filter keeps the opportunities whose latest release is at stage. Releases
 // are oldest first, so the last one is the procedure's current stage.
-func filter(opportunities []*types.Opportunity, stage string) []*types.Opportunity {
+func filter(
+	opportunities []*types.Opportunity, stage string,
+) []*types.Opportunity {
 	var matching []*types.Opportunity
 
 	for _, opportunity := range opportunities {
@@ -63,7 +65,7 @@ func commandOnce(opts *cli.Options) *cobra.Command {
 
 			conf, err := opts.RunSetup(cmd, true, true)
 			if err != nil {
-				return fmt.Errorf("no configuration loaded (%w)", err)
+				return fmt.Errorf("load configuration: %w", err)
 			}
 
 			since, sinceErr := cmd.Flags().GetTime("since")
@@ -96,15 +98,15 @@ func commandOnce(opts *cli.Options) *cobra.Command {
 				filterTag = "award"
 			}
 
-			if len(filterTag) > 0 {
+			if filterTag != "" {
 				results = filter(results, filterTag)
 			}
 
-			jbytes, err := json.MarshalIndent(results, "", "  ")
+			encoded, err := json.MarshalIndent(results, "", "  ")
 			if err != nil {
 				return err
 			}
-			fmt.Println(string(jbytes))
+			fmt.Println(string(encoded))
 
 			return nil
 		},
@@ -118,17 +120,24 @@ func commandOnce(opts *cli.Options) *cobra.Command {
 		"contract updates published since YYYY-MM-DD[ hh:mm:ss]",
 	)
 	cmd.Flags().Bool(
-		"planning", false, "only return planning (i.e. exclude opportunities and awards)",
+		"planning",
+		false,
+		"only return planning (i.e. exclude opportunities and awards)",
 	)
 	cmd.Flags().Bool(
-		"opportunities", false, "only return opportunities (i.e. exclude awards and planning)",
+		"opportunities",
+		false,
+		"only return opportunities (i.e. exclude awards and planning)",
 	)
 	cmd.Flags().Bool(
-		"awards", false, "only return awards (i.e. exclude planning and opportunities)",
+		"awards",
+		false,
+		"only return awards (i.e. exclude planning and opportunities)",
 	)
 	cmd.Flags().Bool(
 		"ignore-rate-limit", false, "ignore the rate limit and fail if exceeded",
 	)
 	cmd.MarkFlagsMutuallyExclusive("planning", "opportunities", "awards")
+
 	return cmd
 }

internal/cli/fetch/once_test.go

@@ -17,7 +17,9 @@ func opp(uuid string, tags ...string) *types.Opportunity {
 	}
 	for _, tag := range tags {
 		o.Releases = append(o.Releases, types.OpportunityRelease{
-			Tags: []types.OpportunityReleaseTag{{Tag: tag}},
+			Tags: []types.OpportunityReleaseTag{{
+				Tag: tag,
+			}},
 		})
 	}
 	return o
@@ -56,6 +58,7 @@ func TestOnceFiltersExclusive(t *testing.T) {
 	cmd.SetArgs([]string{"--planning", "--awards"})
 	cmd.SetOut(io.Discard)
 	cmd.SetErr(io.Discard)
+
 	err := cmd.Execute()
 	if err == nil || !strings.Contains(err.Error(), "none of the others can be") {
 		t.Fatalf("err = %v; want a mutually exclusive flags error", err)

internal/cli/fetch/service.go

@@ -32,7 +32,7 @@ func commandService(opts *cli.Options) *cobra.Command {
 
 			conf, err := opts.RunSetup(cmd, true, foreground)
 			if err != nil {
-				return fmt.Errorf("no configuration loaded (%w)", err)
+				return fmt.Errorf("load configuration: %w", err)
 			}
 
 			since, sinceErr := cmd.Flags().GetTime("since")
@@ -65,5 +65,6 @@ func commandService(opts *cli.Options) *cobra.Command {
 		"contract updates published since YYYY-MM-DD[ hh:mm:ss]",
 	)
 	cmd.Flags().Bool("foreground", false, "run in the foreground")
+
 	return cmd
 }