Create JSON in bash using heredocs

json_example.sh

#!/usr/bin/env bash

var1='value of var1'
var2='value of var2'


read -r -d '' block <<-END
{
    "var1": "${var1}",
    "var2": "${var2}"
}
END

block2=$(cat <<_EOF2_
{
    "var1": "${var1}",
    "var2": "${var2}"
}
_EOF2_
)

echo "$block"
echo $block2