Can not connect to postgresql in libpq

Question

I can't connect to database using this code:

void connect_to_db(){
        connection = PQconnectdb("user=username password=123 dbname=project_db");
        printf("%s\n", PQerrorMessage(connection));

}

int main() {
        connect_to_db();
        PQfinish(connection);
        return 0;
}

when I run the program it prints the error: FATAL: Peer authentication failed for user "username". I had created a database and username with these commands in psql shell:

CREATE DATABASE yourdbname;
CREATE USER youruser WITH ENCRYPTED PASSWORD 'yourpass';
GRANT ALL PRIVILEGES ON DATABASE yourdbname TO youruser;

this is pg_hba.conf file:

# TYPE  DATABASE        USER            ADDRESS                 METHOD

# "local" is for Unix domain socket connections only
local   all             all                                     peer
# IPv4 local connections:
#host    all             all             127.0.0.1/32            ident
host    all     all     127.0.0.1/32        md5
# IPv6 local connections:
#host    all             all             ::1/128                 ident
host    all     all     ::1/128         md5
# Allow replication connections from localhost, by a user with the
# replication privilege.
#local   replication     all                                     peer
#host    replication     all             127.0.0.1/32            ident
#host    replication     all             ::1/128                 ident