Labeled Tab-separated Values (LTSV) format is a variant of 
Tab-separated Values (TSV). Each record in a LTSV file is represented 
as a single line. Each field is separated by TAB and has a label and
 a value. The label and the value have been separated by ':'. With 
the LTSV format, you can parse each line by spliting with TAB (like 
original TSV format) easily, and extend any fields with unique labels 
in no particular order.

go get github.com/Wing924/ltsv

package main

import (
	"fmt"
	"github.com/Wing924/ltsv"
)

func main() {
	line := []byte("foo:123\tbar:456")
    record, err := ltsv.ParseLineAsMap(line, nil)
    if err != nil {
        panic(err)
    }
    fmt.Printf("%#v", record) // map[string]string{"foo":"123", "bar":"456"}
}

$ go test -bench . -benchmem
goos: darwin
goarch: amd64
pkg: github.com/Wing924/ltsv/bench
Benchmark_line_Wing924_ltsv-4          	 2000000	       626 ns/op	     224 B/op	      17 allocs/op
Benchmark_line_Wing924_ltsv_strict-4   	 2000000	       788 ns/op	     224 B/op	      17 allocs/op
Benchmark_line_Songmu_goltsv-4         	  300000	      3975 ns/op	    1841 B/op	      32 allocs/op
Benchmark_line_ymotongpoo_goltsv-4     	  500000	      2286 ns/op	    5793 B/op	      17 allocs/op
Benchmark_line_najeira_ltsv-4          	  300000	      4896 ns/op	    5529 B/op	      26 allocs/op
PASS
ok  	github.com/Wing924/ltsv/bench	8.245s