[Go]os.Stdinへの全件読み込みを複数回すると、2回目以降先頭に余計な改行が必ず入ってきてしまう件

package main

import (
	"bufio"
	"os"
	"strings"
)

func main() {
	sc1 := bufio.NewScanner(os.Stdin)
	buf1 := []string{}
	for sc1.Scan() {
		buf1 = append(buf1, sc1.Text())
	}

	sc2 := bufio.NewScanner(os.Stdin)
	buf2 := []string{}
	for sc2.Scan() {
		buf2 = append(buf2, sc2.Text())
	}

	print("sc1=[", strings.Join(buf1, ";"), "]\n")
	print("sc2=[", strings.Join(buf2, ";"), "]\n")
}

A
B
C
^Z
1
2
3
^Z
sc1=[A;B;C]
sc2=[;1;2;3]

C:\Users\hymko\foo>

package main

import (
	"io/ioutil"
	"os"
)

func main() {
	buf1, _ := ioutil.ReadAll(os.Stdin)
	buf2, _ := ioutil.ReadAll(os.Stdin)
	print("buf1=[", string(buf1), "]\n")
	print("buf2=[", string(buf2), "]\n")
}

C:\Users\hymko\foo\bar>bar
A
B
C
^Z
1
2
3
^Z
buf1=[A
B
C
]
buf2=[
1
2
3
]

#include <stdio.h>
#include <stdlib.h>

char *readstr()
{
    int c;
    char *buffer = NULL;
    size_t size=0;
    while( (c = fgetc(stdin) ) != EOF ){
        buffer = realloc(buffer,size+1);
        buffer[size] = c;
        size++;
    }
    buffer = realloc(buffer,size+1);
    buffer[size+1] = '\0';
    return buffer;
}

int main()
{
    char *buffer1 = readstr();
    char *buffer2 = readstr();

    printf("buffer1=[%s]\n",buffer1);
    printf("buffer2=[%s]\n",buffer2);

    free(buffer1);
    free(buffer2);
}

$ a.exe
A
B
C
^Z
1
2
3
^Z
buffer1=[A
B
C
]
buffer2=[1
2
3
]

package main

import (
	"io/ioutil"
	"os"
)

func main() {
	buf1, _ := ioutil.ReadAll(os.Stdin)
	os.Stdin = os.NewFile(os.Stdin.Fd(), os.Stdin.Name())
	buf2, _ := ioutil.ReadAll(os.Stdin)
	print("buf1=[", string(buf1), "]\n")
	print("buf2=[", string(buf2), "]\n")
}

$ bar
A
B
C
^Z
1
2
3
^Z
buf1=[A
B
C
]
buf2=[1
2
3
]