从Reader.Read（）读取时如何正确清除字节数组

I'm trying to read bytes from a src using Reader.Read but when I print out the data I'm noticing random characters interspersed throughout the output at the beginning of lines which makes me think I'm not clearing the buffer correctly but I'm not sure how to do it being new to Go.

numRead := 1
for numRead > 0 {
    p := make([]byte, 100)
    numRead, _ = hijack.Reader.Read(p) //hijack is a struct that points to a reader
    p = p[:numRead]
    fmt.Printf("%s", p)
}

Some lines come out okay like

Downloaded: https://repo.maven.apache.org/maven2/org/codehaus/mojo/plugin-support/1.0-alpha-1/plugin-support-1.0-alpha-1.pom (5 KB at 25.1 KB/sec)

Others will have a character at the beginning like this

hDownloaded: https://repo.maven.apache.org/maven2/org/apache/apache/4/apache-4.pom (5 KB at 27.4 KB/sec)