Towards the understanding of $Z_c(3900)$ from lattice QCD

Within the framework of three-channel Ross-Shaw effective range theory, we derive the constraints among different parameters of the theory in the case of a narrow resonance close to the threshold of the third channel, which is relevant for the resonance-like structure $Z_c(3900)$. The usage of these constraint relations, together with the multi-channel L"uscher formula in lattice QCD calculations are also discussed and the strategies are outlined.