Segmentation fault when call PQfinish inside singletone pattern

I'm create singletone class, and want to add inside PGconn object.

This class, in the past, will provide connections to DB.

// postgresql
#include <libpq-fe.h>
//==============================================================================
class TestST
{
public:
  static TestST& getInstance()
  {
    static TestST test;
    return test;
  }
  bool createConnection()
  {
    mConn.reset( PQsetdbLogin("localhost", "5432", NULL, NULL,
                             "test_db", "user_app",
                             "passwd"),
                 &PQfinish); // [SIGSEGV when delete] passing a reference to the destroy function
    return true;
  }

private:
  TestST()
  {

  }
private:
  std::shared_ptr<PGconn> mConn; // smart pointer to postgres connetion object
};

//==============================================================================
int main(int argc, char** argv)
{
  TestST::getInstance().createConnection(); // create singletone and connection

  return 0;
}
//==============================================================================

When singletone is deleted, function PQfinish calls signal Segmentation fault. If I move the initialization of mConn to the constructor - it's work. If I build and run on windows (MSVC) - it's work.

postgres version 9.6.9; OS - Debian 9; gcc version 6.3.0