regex multiline mode

Fix the regex pattern in line A, to replace all consecutive 0s to one 0 when 0 is the beginning of the line.The expected output is like:1000101

package main
import (
    "fmt"
    "regexp"
)
func main() {
    s := `100
00
0
1
0
0
1`
    pattern := regexp.MustCompile("0(0|\n)*0") //A
    s = pattern.ReplaceAllString(s, "0")
    fmt.Println(s)
}

Answer

package main
import (
    "fmt"
    "regexp"
)
func main() {
    s := `100
00
0
1
0
0
1`
    pattern := regexp.MustCompile("(?m:^0(0|\n)*0)")
    s = pattern.ReplaceAllString(s, "0")
    fmt.Println(s)
}