chore(parsers): Fix linter issues

plugins/parsers/binary/parser.go

@@ -85,7 +85,7 @@ func (p *Parser) Parse(data []byte) ([]telegraf.Metric, error) {
 	}
 
 	matches := 0
-	metrics := make([]telegraf.Metric, 0)
+	metrics := make([]telegraf.Metric, 0, len(p.Configs))
 	for i, cfg := range p.Configs {
 		// Apply the filter and see if we should match this
 		if !cfg.matches(buf) {
@@ -151,7 +151,7 @@ func extractPart(in []byte, offset, bits uint64) ([]byte, error) {
 		return nil, fmt.Errorf("out-of-bounds @%d with %d bits", offset, bits)
 	}
 
-	var out []byte
+	out := make([]byte, 0, length)
 	out = append(out, in[start:start+length]...)
 
 	if offset%8 != 0 {

plugins/parsers/csv/parser.go

@@ -334,7 +334,7 @@ func parseCSV(p *Parser, r io.Reader) ([]telegraf.Metric, error) {
 		return nil, err
 	}
 
-	metrics := make([]telegraf.Metric, 0)
+	metrics := make([]telegraf.Metric, 0, len(table))
 	for _, record := range table {
 		m, err := p.parseRecord(record)
 		if err != nil {

plugins/parsers/nagios/parser.go

@@ -190,9 +190,10 @@ func (p *Parser) Parse(buf []byte) ([]telegraf.Metric, error) {
 }
 
 func parsePerfData(perfdatas string, timestamp time.Time) ([]telegraf.Metric, error) {
-	metrics := make([]telegraf.Metric, 0)
+	unParsedPerfs := perfSplitRegExp.FindAllString(perfdatas, -1)
+	metrics := make([]telegraf.Metric, 0, len(unParsedPerfs))
 
-	for _, unParsedPerf := range perfSplitRegExp.FindAllString(perfdatas, -1) {
+	for _, unParsedPerf := range unParsedPerfs {
 		trimmedPerf := strings.TrimSpace(unParsedPerf)
 		perf := nagiosRegExp.FindStringSubmatch(trimmedPerf)
 

plugins/parsers/wavefront/parser.go

@@ -45,7 +45,7 @@ type PointParser struct {
 
 // NewWavefrontElements returns a slice of elementParser's for the Graphite format
 func NewWavefrontElements() []elementParser {
-	var elements []elementParser
+	elements := make([]elementParser, 0, 7)
 	wsParser := whiteSpaceParser{}
 	wsParserNextOpt := whiteSpaceParser{nextOptional: true}
 	repeatParser := loopedParser{wrappedParser: &tagParser{}, wsParser: &wsParser}
@@ -128,7 +128,7 @@ func (p *Parser) SetDefaultTags(tags map[string]string) {
 }
 
 func (p *PointParser) convertPointToTelegrafMetric(points []Point) ([]telegraf.Metric, error) {
-	metrics := make([]telegraf.Metric, 0)
+	metrics := make([]telegraf.Metric, 0, len(points))
 
 	for _, point := range points {
 		tags := make(map[string]string)